Obesity: Role of Environmental Chemicals

Transcription

1 Obesity: Role of Environmental Chemicals Jerrold J. Heindel, Ph.D. National Institute of Environmental Health Sciences

2 Overview History Background information on obesity: setting the stage Examples of environmental chemicals and obesity Data gaps and needs

3 A Little History Ballei-Hamilton, Chemical toxins: a hypothesis to explain the global obesity epidemic, J Alt and Comp Med, 2002 Heindel: Endocrine Disruptors and the Obesity Epidemic, Commentary, Tox Sci, NIEHS PAR: The fetal basis of adult disease: role of the environment Levin and Heindel, Obesity: fetal origins and environmental influences, Duke Integrated Toxicology Program and NIEHS sponsored symposium, Bruce Blumberg coined Obesogen NIEHS PAR: Role of environmental chemical exposures in the development of obesity, type 2 diabetes, and metabolic syndrome (R21 and R01) Obesity grantee meeting Metabolic disruptor meeting, Parma

4 Synthetic Chemical Production (billion kg/annum) Percent Overweight Adults Chemical Toxins: A Hypothesis to Explain The Global Obesity Epidemic Chemical Production % Overweight Adults Baillie-Hamilton 2002 Years Baillie-Hamilton, 2002

5 Numerous Chemicals Produce Weight Gain Pesticides (Chadwick et al., 1988; Deichmann et al., 1972; Deichmann et al., 1975; Dorgan et al., 1999; Hovinga et al., 1993; Stellman et al., 1997; Takahama et al., 1972; Villeneuve et ai., 1977) Organophosphates (Breslin et al., 1996; Cranmer et al., 1978; Nicolau, 1983; Tran-kina et al., 1985) Carbamates (Walker et al., 1994; Yen et al., 1984) Polychlorinated biphenyls (Clark, 1981; Dar et al., 1992; Hovinga et al., 1993) Polybrominated biphenyls, fire retardants (Gupta et al., 1983) Plastics, phthalates, and bisphenol A (Ema et al., 1990; Howdeshell et. al., 1999; Rubin et al., 2001) Heavy metals, such as cadmium and lead (Antonio et al., 1999; Hovinga et al., 1993) Solvents (Chu et al., 1986; Gaworski et al., 1985; Hardin et al., 1987; Moser et al., 1995; Wahlberg, 1979) Baillie-Hamilton 2002

6 A Little History Ballei-Hamilton, Chemical toxins: a hypothesis to explain the global obesity epidemic, J Alt and Comp Med, 2002 Heindel: Endocrine Disruptors and the Obesity Epidemic, Commentary, Tox Sci, NIEHS PAR: The fetal basis of adult disease: role of the environment Levin and Heindel, Obesity: fetal origins and environmental influences, Duke Integrated Toxicology Program and NIEHS sponsored symposium, Blumberg coined Obesogen NIEHS PAR: Role of environmental chemical exposures in the development of obesity, type 2 diabetes, and metabolic syndrome (R21 and R01) Obesity grantee meeting Metabolic disruptor meeting, Parma

7 Causes of Weight Gain (Multifactorial) Genetic background Congenital Illness (Hypothyroidism, Cushing s Syndrome) Drug use (Thiazolinedione antidiabetics; Tricyclic antidepressants; Selective serotonin uptake inhibitors; Atypical anti-psychotic drugs) Viruses (Adenovirus 36) Antibiotics Environment (Lack of exercise; Lack of sleep; Microbiome; Stress (increased glucocorticoids); Nutrition (sugar, fats, additives); Environmental chemicals)

8 Control of Weight: An Endocrine Issue Hedonic Pathway; Reward, craving addiction Homeostatic Pathway; Appetite and satiety Weight gain is controlled by the endocrine system. Thus it is sensitive to disruption by endocrine disrupting chemicals. Badman and Flier, Science, 2005

9 Endocrine Disruptors Defined An exogenous chemical, or mixture of chemicals, that interferes with any aspect of hormone action (Zoeller et al., Endocrine Society Position Statement, Endocrinology 153: , 2012)

10 Current use Pesticides Endocrine Disrupting Chemicals Flame Retardants Plastics Herbicides Industrial byproducts Plasticizers Personal Care Products Surfactants Cosmetics Solvents Sunscreens Antioxidants Heavy Metals Persistant Organic Pollutants Polycyclic aromatic Compounds

11 We All Carry a Chemical Body Burden 287 chemicals in cord blood The presence of chemicals in the womb does not mean that they are causing harm. 47 chemicals in every pregnant woman tested In breast milk (PCBs, dioxins, pesticides, mercury, flame retardants) However, it does mean that we have accepted a strategy whereby every pregnant woman is contaminated with chemicals, without her knowledge with the potential for harm. Of people tested by CDC: BPA in 93% Phthalates 50-97% PFCs in 91-99% PBDEs in 100% Triclosan in 80% PCBs in 100%

12 Developmental Origins of Disease It is clear that developmental exposures to environmental chemicals can lead to a variety of diseases/dysfunctions later in life. Sensitivity to develop obesity also has its origins during development ( in utero and early childhood) with some effects during adulthood. What is the role of environmental chemical exposures?

13 Developmental Basis of Obesity: Obesogen Hypothesis An emerging hypothesis that the obesity epidemic is due, in part, to environmental exposures during development We hypothesize that there is a subset of endocrine disruptors, obesogens, that can act during development to Disrupt Food adipose intake and tissue exercise development are important but environmental Via an increase chemicals the number can alter of fat the cells set-point for gaining weight how much food it takes to put on Alter food intake and metabolism weight and also how much exercise is needed to Via effects on pancreas, adipose tissue, liver, GI tract, reduce brain and/or weight muscle via alterations in developmental programming. thereby altering the programming of the setpoint or sensitivity for developing obesity later in life.

14 Proof of Principle: Effect of Maternal Smoking during Pregnancy on Childhood Weight at School Entry % never smoked (n = 3,847) < 10 cigarettes per day (n = 638) > = 10 cigarettes per day (n = 110) Risk Estimate 0 BMI>90. Perz. Overweight BMI>97. Perz. Obese von Kries et al., 2002

15 Proof of Principle: Developmental Exposure to DES Control DES 1 Month 4 Month Exposure of CD-1 mice to DES for 5 days at birth resulted in increased weight gain starting at puberty in female mice. No change in food intake or exercise. Non-monotonic dose response Newbold et al.

16 Fat (%) Lean (%) Developmental BPA Exposure and Weight Gain Percent Fat PND50 PND90130 Day Contro l 0.25ug 2.5ug 25ug Animal Studies Multiple labs Multiple species Sex differences Dose range (10ug/kg-70ug/kg) Human Studies Cross sectional: adults and children Prospective PND50 Percent Lean PND Day N=12-14/gp GD18-Lactational day 16 CD-1 Males Greenberg and Rubin (unpublished data)

17 Developmental Exposure to BPA Affects Brain Satiety Centers Fetal BPA exposure Appetite (NPY) neurons Satiety (POMC) neurons Increased Food Intake Ross and Desai, unpub Weight Gain

18 Body weight at 12 wks (g) F1 offspring Developmental DEHP Exposure Increases Visceral Fat Tissue and Adipocyte Number Control 0.05 mg DEHP ;;;;;;;;;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;; 5 mg DEHP 500 mg DEHP DEHP (mg/kg bw/d) Schmidt et al., EHP, 2012

19 Examples of Published Human Studies Gladen et al, Prenatal & early life exposures to low levels of PCBs and DDE are associated with increased weight in boys and girls at puberty,j. Pediatr., ( Smink et al, Exposure to hexachlorobenzene during pregnancy increases the risk of overweight in children aged 6 years, Acta Paediatrica, 2008 Verhulst et al, Intrauterine exposure to environmental pollutants (POPs) and body mass during the first 3 years of life, EHP, 2009 Syme et al, Prenatal exposure to maternal cigarette smoking and accumulation of intra-abdominal fat during adolescence, Obesity, 2010 Halldorsson et al, Prenatal exposure to perfluooctanoate and the risk of overweight at 20 years of age: a prospective cohort study, EHP, 2012 Runde et al, Association of childhood obesity with maternal exposure to ambient air polycyclic aromatic hydrocarbons during pregnancy AJ, 2012 Cupul-Uicab et al Prenatal exposure to persistent organochlorines and childhood obesity in the US collaborative perinatal project, EHP, 2013 Harley KG et al, Prenatal and postnatal bisphenol A exposure and body mass index in childhood in the SHAMACOS cohort, EHP, 2013 Valvi et al, Prenatal bisphenol A urine concentration and early rapid growth and overweight risk in the offspring, Epidemiology, 2013 Warner et al, Prenatal exposure to dichlorodiphenyltrichloroethane and obesity at 9 years of age in the CHAMACOS study cohort, AJM, 2014

20 Adjusted Mean BMI Z-score Prenatal PAH Exposure is Associated with BMI Z-score at Age 5 & BMI Z-score at age 5 P for trend = 0.01, n=422 BMI Z-score at age 7 P for trend = 0.04, n= Prenatal Ambient Air PAH Exposure (Ng/M 3 ) Adjusted for age, gender, ethnicity, birth weight, maternal obesity and maternal receipt of public assistance [Rundle et al., AJE, 2012]

21 Epigenetic Transgenerational Inheritance of Obesity Positive results Tributyl tin (M and F) DDT (M and F) Hydrocarbon mixture (jet fuel) (M and F) BPA DEHP, DBP (M and F) Negative results Permethrin/DEET mixture Vinclozolin Dioxin Exposure (F0) Assess Weight Gain (F4)

22 Obesogens Just the Tip of the Iceberg? Triflumizole ( fungicide) PFOA Estradiol Genistein Lead PCBs Phthalates DES Nicotine Air Pollution Organophosphate Pesticides (Parathion, Diazinon, Chlorpyrifos) Tributyltin PBDEs Bisphenol A Organochlorine Pesticides (DDT/DDE, HCB) Monosodium Glutamate Artificial Sweeteners Benzo[a]pyrene (PAH) Fructose? Some Drugs

23 Current NIEHS Obesity/Diabetes Funding 57 total grants (P01, R01, R03, R21, U01) currently funded to address obesity and diabetes Of funded obesity and diabetes grants: 20 work with animal models 5 are basic cellular/molecular studies 32 work with human cohorts, and exposures studied are different for adult versus birth cohorts Exposures Studied: Adult Cohorts Air Pollutants Chlorinated Compounds Fluorinated Compounds Metals Nutrition / Diet Pesticides (12) Particulates Traffic Pollutants NO / NO2 PCBs Dioxins Hexachlorobenzene PFCs PFOAs PFOSs Arsenic High fat diet Chlorinated Pesticides Exposures Studied: Birth Cohorts Hormonal Mimics BPA Phthalates Other EDCs DES Air Pollutants Particulates Traffic Pollutants PAHs Metals Arsenic Lead Cadmium Copper Mercury Nutrition / Diet High fat diet Fluorinated Compounds (20) PFCs PFOA PFOS Chlorinated PCBs Compounds Triclosan Perchlorates Chlorinated Pesticides pesticides Psychosocial Stress

24 Data Gaps and Needs This obesogen field is less than 10 years old thus there is a long list of data needs/questions to be answered. Determine which chemicals have ability to cause weight gain (characteristics)? Screens to detect and prioritize Define dose responses (internal doses), timing, sites and mechanism(s). Assess multiple chemicals and integrate with other stressors. Measure multiple overlapping endpoints: diabetes, liver function, muscle metabolism, brain satiety, GI effects, inflammation. Coordinate animal studies and endpoints with human cohort studies.improved interactions between epidemiologists and animal researchers. Improve exposure assessments in human studies integrate genetics and environmental exposures to disease onset and severity. Prove altered setpoint or susceptibility hypothesis. Hold Grantee meetings Integrate into field of obesity research and prevention.

25 We hold our future in our hands and it is our children The End.but just the beginning